The safety hoods described are preferably used together with blower filter systems. Such blower filter systems are designed for light and medium breathing protection and support the user during the use of use of breathing filters by reducing the breathing resistance, contrary to conventional breathing masks, and thus make possible a long, fatigue-free use.
Such a blower filter system usually has a blower filter device being carried on the belt and a breathing port, which is designed as a hood, helmet or mask. The individual components are connected with one another, as a rule, by means of a flexible tube. The polluted or contaminated air is drawn in by means of a blower and is made available to the user via a filter. At least the face, partially the entire head, neck and the shoulders are protected from contamination in case of the use of hoods as a breathing port. Hoods for blower filter devices are manufactured, as a rule, from a flexible material and have a port, which is often arranged in the nuchal area of the user and via which the purified air flows into the interior space of the hood.
The hood is transparent in the field of vision of the user in order for the user to be able to optically perceive the area surrounding him. The visor pane of the respirator hood is located in this field of vision of the user.
A respirator hood, which can be combined with a blower filter device, is described in WO 2009/070403 A1. The hood has essentially a head strap for fixing the hood on the head of the user, a flexible outer skin, which surrounds the head and partially the face of the user, as well as a visor pane, which is arranged in the field of vision of the user and is connected with the flexible outer skin. Further, a porous material, which assumes the function of an exhalation valve, is provided in some areas beneath the visor pane in the chin area of the respirator hood, so that the air exhaled by the user, which is enriched with CO2, is released into the surrounding area. The air flows within the hood from a circular air inlet, which is connected with an externally connected flexible tube, at first into the area of the nape or the back of the head of the user and subsequently into the facial space over the head.
To fix the visor pane on the head strap, the carrying ring of the strap has two fastening elements. These two fastening elements are arranged in the area of the lateral edges of the visor pane, so that a free space is created between the carrying ring of the strap and the visor pane, which shall guarantee good flow of the air, in the area of the user's forehead.
A respirator hood of this class is described, further, in U.S. Pat. No. 6,367,085 B1. The visor pane is connected with the strap in this case as well, and a total of four fastening points are provided, two of which are located in the area of the user's forehead and two in the area of the outer edges of the visor pane. Since the visor pane is fastened to the head strap in this technical solution in the outer area, on the one hand, but, moreover, also in the area of the user's forehead, this type of fastening represents a comparatively rigid connection between the head strap and the visor pane.
It is common to the prior-art respirator hoods that the fastening of the visor pane on the strap always takes place in the area of the outer edges of the visor panes, and the visor pane is often connected in this area with the carrying ring of the strap. The visor pane is bent due to this kind of fastening, so that a free space, which shall guarantee good flow of the air, develops between the user's face and the visor pane. However, the adjustment of the head strap, especially of the carrying ring, varies depending on the size of the head as well as the shape of the head of the user, so that the free space between the head strap and the visor pane may also be different or different curvatures of the visor pane will develop depending on the size and shape of the user's head.
It is therefore often problematic in the prior-art fastenings for visor panes in respirator hoods that the properties of the air flow change as a function of the free space that becomes established between the head strap and the visor pane and the air flow that becomes established in the area of the face is partially felt as being unpleasant, especially when a comparatively strong air flow is flowing over the eyes. The eyes may dry out and become irritated because of such forms of flow, especially when using a respirator hood over a rather long time. Furthermore, the field of vision may decrease and unwanted reflection phenomena may occur because of the radius of curvature that becomes established because of the different radii of curvature. Moreover, great curvature of the visor pane may lead to comparatively great stresses within the visor pane, which may comparatively easily lead to slipping of the respirator hood during use. This represents a considerable limitation in respect to work safety as well as wearing comfort.